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Padrões atmofésricos associados a concentrações de ozônio troposférico na região metropolitana de São Paulo; Atmospheric patterns associated with concentrations of tropospheric ozone in the metropolitan region of Sao Paulo

Chiquetto, Júlio Barboza
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 04/03/2009 Português
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Nos últimos anos, tem-se observado que na RMSP o ozônio troposférico foi o poluente responsável pela maior parte das ultrapassagens dos padrões de qualidade do ar estabelecidos pela CETESB. Supõe-se que diferentes padrões atmosféricos possam interferir nas concentrações de ozônio, devido à influência na variabilidade da concentração de poluentes, já estudada, e devido ao fato deste poluente ser formado pela interação entre seus precursores e a radiação solar. Dados horários de ozônio, provenientes de 17 estações da rede de monitoramento de poluentes da CETESB, foram utilizados para a construção de séries de médias anuais, mensais e diárias. O ciclo sazonal médio do ozônio, para a região de estudo, indicou um máximo em meados da primavera e mínimo no final do outono, o que é fortemente influenciado pelo ciclo médio de radiação solar e cobertura de nuvens. As estações situadas em áreas com reduzida atividade urbana e longe do centro da mancha urbana apresentaram ciclo sazonal mais bem definido e concentrações sobremaneira mais altas, sugerindo que as concentrações absolutas e o ciclo sazonal do ozônio sejam influenciados pelo uso do solo no entorno da estação. Os meses com anomalias positivas e negativas intensas de ozônio foram selecionados...

Influence of NO2 and metal ions on oxidation of aqueous-phase S(IV) in atmospheric concentrations

Martins,Cláudia R.; Alves,Janete J.F.; Carvalho,Wanessa B.D.; Cardoso,Cristiane S.C.; Andrade,Jailson B. de
Fonte: Academia Brasileira de Ciências Publicador: Academia Brasileira de Ciências
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2008 Português
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An investigation was made of the influence of atmospheric concentrations (15 or 130 ppbv) of NO2 on the aqueous-phase oxidation rate of S(IV) in the presence and absence of Fe(III), Mn(II) and Cr(VI) metal ions under controlled experimental conditions (pH, T, concentration of reactants, etc.). The reaction rate in the presence of the NO2 flow was slower than the reaction rate using only clean air with an initial S(IV) concentration of 10-4 mol/L. NO2 appears to react with S(IV), producing a kind of inhibitor that slows down the reaction. Conversely, tenfold lower concentrations of S(IV) ([S(IV)]º = 10-5 mol/L) caused a faster reaction in the presence of NO2 than the reaction using purified air. Under these conditions, therefore, the equilibrium shifts to sulfate formation. With the addition of Fe(III), Mn(II) or Cr(VI) in the presence of a NO2 flow, the reaction occurred faster under all the conditions in which S(IV) oxidation was investigated.

Size distribution of atmospheric particulate ionic species at a coastal site in Portugal

Alves,Célia; Pio,Casimiro; Campos,Eduarda; Barbedo,Patrícia
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2007 Português
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A Berner impactor was used to collect size-differentiated aerosol samples from March to August 2003 in the city of Aveiro, on the Portuguese west coast. The samples were analysed for the main water-soluble ion species. The average concentration of sulphate, nitrate, chloride and ammonium was 6.38, 3.09, 1.67 and 1.27 µg m-3, respectively. The results show that SO4(2-) and NH4+ were consistently present in the fine fraction < 1 µm, which represents, on average, 72 and 89% of their total atmospheric concentrations, respectively. The NO3-particles were concentrated in the coarse size. Chloride presented the characteristic coarse mode for marine aerosols. During some spring/summer events, an ammonium surplus was observed (NH4+/SO4(2-) molar ratios > 2), possibly due to greater availability of ammonia coming from agricultural activities or from the neighbouring chemical industrial complex. During the remaining periods, the aerosol was found to be somewhat acidic and predominantly in the form of ammonium bisulphate (NH4+/SO4(2-) molar ratios = 0.5-1.25). Samples collected under a major or exclusive influence of maritime air masses were essentially constituted by coarse particles with enrichment in sea salt, while for air masses of continental origin the contribution of water-soluble ionic species in the fine mode was more pronounced.

Exploration of the Potential Energy Surfaces, Prediction of Atmospheric Concentrations, and Prediction of Vibrational Spectra for the HO2···(H2O)n (n=1-2) Hydrogen Bonded Complexes

Alongi, Kristin S.; Dibble, Theodore S.; Shields, George C.; Kirschner, Karl N.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 16/03/2006 Português
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The hydroperoxy radical (HO2) plays a critical role in Earth’s atmospheric chemistry as a component of many important reactions. The self-reaction of hydroperoxy radicals in the gas phase is strongly affected by the presence of water vapor. In this work we explore the potential energy surfaces of hydroperoxy radicals hydrogen bonded to one or two water molecules, and predict atmospheric concentrations and vibrational spectra of these complexes. We predict that when the HO2 concentration is on the order of 108 molecules·cm-3 at 298K, that the number of HO2···H2O complexes is on the order of 107 molecules·cm-3 and the number of HO2···(H2O)2 complexes is on the order of 106 molecules·cm-3. Using the computed abundance of HO2···H2O, we predict that, at 298K, the bimolecular rate constant for HO2···H2O + HO2 is about ten times that for HO2 + HO2.

Global Budget of Methanol: Constraints from Atmospheric Observations

Jacob, Daniel J.; Field, Brendan D.; Li, Qinbin; Blake, Donald R.; de Gouw, Joost; Warneke, Carsten; Hansel, Armin; Wisthaler, Armin; Singh, Hanwant B.; Guenther, A.
Fonte: American Geophysical Union Publicador: American Geophysical Union
Tipo: Artigo de Revista Científica
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We use a global three-dimensional model simulation of atmospheric methanol to examine the consistency between observed atmospheric concentrations and current understanding of sources and sinks. Global sources in the model include 128 Tg yr−1 from plant growth, 38 Tg yr−1 from atmospheric reactions of CH3O2 with itself and other organic peroxy radicals, 23 Tg yr−1 from plant decay, 13 Tg yr−1 from biomass burning and biofuels, and 4 Tg yr−1 from vehicles and industry. The plant growth source is a factor of 3 higher for young than from mature leaves. The atmospheric lifetime of methanol in the model is 7 days; gas-phase oxidation by OH accounts for 63% of the global sink, dry deposition to land 26%, wet deposition 6%, uptake by the ocean 5%, and aqueous-phase oxidation in clouds less than 1%. The resulting simulation of atmospheric concentrations is generally unbiased in the Northern Hemisphere and reproduces the observed correlations of methanol with acetone, HCN, and CO in Asian outflow. Accounting for decreasing emission from leaves as they age is necessary to reproduce the observed seasonal variation of methanol concentrations at northern midlatitudes. The main model discrepancy is over the South Pacific, where simulated concentrations are a factor of 2 too low. Atmospheric production from the CH3O2 self-reaction is the dominant model source in this region. A factor of 2 increase in this source (to 50–100 Tg yr−1) would largely correct the discrepancy and appears consistent with independent constraints on CH3O2 concentrations. Our resulting best estimate of the global source of methanol is 240 Tg yr−1. More observations of methanol concentrations and fluxes are needed over tropical continents. Better knowledge is needed of CH3O2 concentrations in the remote troposphere and of the underlying organic chemistry.; Earth and Planetary Sciences

Estimation of methane and carbon dioxide surface fluxes using a 3-D global atmospheric chemical transport model; Estimation of CH₄ and CO₂ surface fluxes using a 3-D global atmospheric chemical transport model

Chen, Yu-Han, 1973-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 180 p.; 13310016 bytes; 13332590 bytes; application/pdf; application/pdf
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Methane (CH₄) and carbon dioxide (CO₂) are the two most radiatively important greenhouse gases attributable to human activity. Large uncertainties in their source and sink magnitudes currently exist. We estimate global methane surface emissions between 1996 and 2001, using a top-down approach that combines observed and simulated atmospheric CH₄ concentrations. As a secondary study, we describe our participation in a CO₂ inverse-modeling intercomparison. The available methane time-series data used in this work include observations from 13 high-frequency stations (in-situ) and 74 low-frequency sites (flask). We also construct an annually-repeating reference emissions field from pre-existing datasets of individual methane processes. For our forward simulations, we use the 3-D global chemical transport model MATCH driven by NCEP meteorology. A prescribed, annually-repeating OH field scaled to fit methyl chloroform observations is used as the methane sink. A total methane source of approximately 600 Tg yr⁻¹ best reproduces the methane growth rate between 1993-2001. Using the reference emissions, MATCH can reproduce the observed methane variations at many sites. Interannual variations in transport, including those associated with ENSO and the NAO...

Mechanistic, sensitivity, and uncertainty studies of the atmospheric oxidation of dimethylsulfide

Lucas, Donald David, 1969-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 249 p.; 13305935 bytes; 13305736 bytes; application/pdf; application/pdf
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The global-scale emissions and reactivity of dimethylsulfide (CH3SCH3, DMS) make it an integral component in the atmospheric sulfur cycle. DMS is rapidly oxidized in the atmosphere by a complex gas-phase mechanism involving many species and reactions. The resulting oxidized sulfur-bearing products are hygroscopic and interact with aerosols through condensation and secondary aerosol formation. Predictions of the impacts of DMS chemistry on aerosols and climate are inhibited by the poorly understood DMS oxidation mechanism. This thesis diagnoses the gas-phase connections between DMS and its oxidation products by simulating comprehensive DMS chemistry (approximately 50 reactions and 30 species) using three atmospheric models of varying size and complexity. A diurnally-varying box model of the DMS cycle in the remote marine boundary layer is used to identify important DMS-related parameters and propagate parameter uncertainties to the sulfur-containing species. This analysis shows that the concentrations of DMS and sulfur dioxide (SO2) are sensitive to relatively few parameters. Moreover, the concentrations of DMS and SO2 are found to have factor of 2 uncertainties caused primarily (more than 60% of the variance) by uncertainties in DMS emissions and heterogeneous removal...

Optimal estimation of the surface fluxes of chloromethanes using a 3-D global atmospheric chemical transport

Xiao, Xue, Ph. D. Massachusetts Institute of Technology
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 210 p.
Português
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The four chloromethanes - methyl chloride (CH3Cl), dichloromethane (CH2Cl2), chloroform (CHCl3), and carbon tetrachloride (CCl4), are chlorine-containing gases contributing significantly to stratospheric ozone depletion and having adverse health effects. Large uncertainties in estimates of their source and sink magnitudes and temporal and spatial variations currently exist. GEIA inventories and other bottom-up emission estimates are used to construct a priori maps of surface fluxes of these species. The Model of Atmospheric Transport and CHemistry (MATCH), driven by NCEP interannually varying meteorological fields, is then used to simulate the trace gas mole fractions using the a priori emissions and to quantify the time series of sensitivities of tracer concentrations to different aseasonal, seasonal, and regional sources and sinks.We implement the Kalman filter (with the unit pulse response method) to estimate both constant (if applicable) and time-varying surface fluxes on regional/global scales at a monthly resolution for the three short-lived species between 2000-2004, and the continental industrial emissions and global oceanic sink for CCl4 at a 3-month resolution between 1996-2004. The high frequency observations from AGAGE...

Beyond Mitigation : Potential Options for Counter-Balancing the Climatic and Environmental Consequences of the Rising Concentrations of Greenhouse Gases

MacCracken, Mike
Fonte: Banco Mundial Publicador: Banco Mundial
Português
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Global climate change is occurring at an accelerating pace, and the global greenhouse gas (GHG) emissions that are forcing climate change continue to increase. Given the present pace of international actions, it seems unlikely that atmospheric composition can be stabilized at a level that will avoid "dangerous anthropogenic interference" with the climate system, as called for in the UN Framework Convention on Climate Change. Complicating the situation, as GHG emissions are reduced, reductions in the offsetting cooling influence of sulfate aerosols will create an additional warming influence, making an early transition to climate stabilization difficult. With significant reductions in emissions (mitigation) likely to take decades, and with the impacts of projected climate change-even with proactive adaptation-likely to be quite severe over the coming decades, additional actions to offset global warming and other impacts have been proposed as important complementary measures. Although a number of possible geoengineering approaches have been proposed...

A Financing Facility for Low-Carbon Development

de Gouvello, Christophe; Zelenko, Ivan; Ambrosi, Philippe
Fonte: World Bank Publicador: World Bank
Português
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The reality of climate change associated with anthropogenic emissions is now widely acknowledged by the scientific community. Its potential devastating future harms are equally well perceived and as stated in the Copenhagen Accord major nations agree on the need to jointly and urgently combat climate change. The international community is also quite aware that stabilizing atmospheric concentrations of green-house gases (GHG) at supportable levels will require a drastic reduction in GHG emissions within a limited period of time. Undertaking such an enormous effort triggers several interlinked challenges: (1) technically mitigating GHG emissions to the required level; (2) implementing these solutions in countries where the required amount of emission reduction is most realistically and efficiently achievable in particular through involving and using in full the large potential of developing countries; and (3) mobilizing the large amount of financing needed to ensure that the corresponding projects and programs can be effectively implemented. Furthermore...

Atmospheric Stabilization of CO2 Emissions : Near-term Reductions and Intensity-based Targets

Timilsina, Govinda R.
Fonte: World Bank, Washington, DC Publicador: World Bank, Washington, DC
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This study analyzes CO2 emissions reduction targets for various countries and geopolitical regions by the year 2030 in order to stabilize atmospheric concentrations of CO2 at the level of 450 ppm (550 ppm including non CO2 greenhouse gases). It also determines CO2 intensity cuts that would be needed in those countries and regions if the emission reductions were achieved through intensity-based targets while assuming no effect on forecasted economic growth. Considering that the stabilization of CO2 concentrations at 450 ppm requires the global trend of CO2 emissions to reverse before 2030, this study develops two scenarios: reversing the global CO2 trend in (i) 2020 and (ii) 2025. The study shows that global CO2 emissions would be 42 percent above the 1990 level in 2030 if the increasing trend of global CO2 emissions is reversed by 2020. If reversing the trend is delayed by 5 years, the 2030 global CO2 emissions would be 52 percent higher than the 1990 level. The study also finds that to achieve these targets while maintaining assumed economic growth...

Atmospheric Concentrations and Deposition of Polycyclic Aromatic Hydrocarbons to the Mid-Atlantic East Coast Region

GIGLIOTTI Cari; TOTTEN Lisa; OFFENBERG John; DACHS Jordi; REINFELDER John R.; NELSON Eric D.; GLENN IV Thomas R.; EISENREICH STEVEN
Fonte: AMER CHEMICAL SOC Publicador: AMER CHEMICAL SOC
Tipo: Articles in Journals Formato: Printed
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Atmospheric concentrations of polycyclic aromatic hydrocarbons (PAHs) were measured at urban/industrial, suburban, coastal, and rural areas in New Jersey as part of the New Jersey Atmospheric Deposition Network. Concentrations of 36 PAH compounds were measured in the gas and particle phases in air and in precipitation at nine sites at regular intervals from October 1997 through May 2001. Gas-phase and particle-phase SUM 36PAH concentrations ranged from 0.45 to 118 ng/m3 and from 0.046 to 172 ng/m3, respectively, and precipitation concentrations ranged from 11 to 16200 ng/L. PAH concentrations vary spatially across the region, with the highest concentrations occurring at the most heavily urban and industrial locations. Average gas absorption deposition ranged from 0.004 (naphthacene) to 5040 (methylphenanthrenes) ng/m2 d, and dry particle deposition PAH fluxes ranged from 0.11 (naphthacene) to 300 (benzo[b+k]fluoranthene) ng/m2 d at the nine sites. Average atmospheric wet deposition PAH fluxes at the seven sites ranged from 0.40 (cyclopenta-[cd]pyrene) to 140 (methylphenanthrenes) ng/m2 d. These represent the first comprehensive estimates of PAH deposition to New Jersey and the Mid-Atlantic East Coast.; JRC.H.5-Rural, water and ecosystem resources

Atmospheric occurrence, transport and deposition of polychlorinated biphenyls and hexachlorobenzene in the Mediterranean and Black Seas

BERROJALBIZ Naiara; CASTRO-JIMENEZ Javier; MARIANI Giulio; WOLLGAST Jan; HANKE Georg; DACHS J.
Fonte: COPERNICUS GESELLSCHAFT MBH Publicador: COPERNICUS GESELLSCHAFT MBH
Tipo: Articles in Journals Formato: Printed
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Abstract. The Mediterranean and Black Seas are unique marine environments subject to important anthropogenic pressures due to direct and indirect loads of atmospheric inputs of organochlorine compounds (OCl) from primary and secondary sources. Here we report the results obtained during two east-west sampling cruises in June 2006 and May 2007 from Barcelona to Istanbul and Alexandria, respectively, where gas phase and aerosol samples were collected. Both matrices were analyzed for 41 polychlorinated biphenyls (PCBs), including dioxin-like congeners, and hexachlorobencene (HCB). The values reported in this study for gas phase HCB and ∑41PCB (LOD to 418.3 pg m−3 and from 81.99 to 931.6 pg m−3 respectively) are in the same range of those reported in former studies, possibly suggesting a limited decline in their atmospheric concentrations during the last decade for the Mediterranean region due to land base OCl sources. There is a clear influence of the direction of the air-mass on the atmospheric concentrations of PCBs, with higher concentrations when the air mass was from southern Europe, and the lowest concentrations for air masses coming from the SW Mediterranean and Atlantic Ocean. PCBs and HCB are close to air–water equilibrium for most sampling periods...

Atmospheric concentrations, occurrence and deposition of persistent organic pollutants (POPs) in a Mediterranean coastal site (Etang der Tau, France)

CASTRO JIMENEZ Javier; MARIANI Giulio; VIVES-RUBIO Ingrid; SKEJO Helle; UMLAUF Gunther; ZALDIVAR COMENGES Jose'; DUERI Sibylle; MESSIAEN G.; LAUGIER T.
Fonte: ELSEVIER SCI LTD Publicador: ELSEVIER SCI LTD
Tipo: Articles in Journals Formato: Printed
Português
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47.23455%
Atmospheric concentrations and deposition fluxes (wet and dry) of PCDD/F, PCB and PBDE to a Mediterranean coastal location (Thau lagoon, France) have been evaluated. ∑2,3,7,8-PCDD/Fs, ∑18 PCBs and ∑8 PBDEs (gas + particulate) air concentrations ranged from 67-1700 fg m-3, 13-95 and 158-230 pg m-3, respectively. Air masses origin and composition as well as local meteorological conditions play a role in pollutant loadings into the Thau lagoon airshed and subsequent inputs to the aquatic system. Whereas PCDD/Fs may arrive to the area transported from other regions as well as locally emitted, PCB and PBDEs inputs seem to me more related to local emissions. Total (wet + dry) Σ2,3,7,8-PCDD/Fs, Σ18PCBs, and Σ8PBDEs (dry only) mass inputs to Thau Lagoon waters are 3, 18, and 16 g y-1, respectively. The observed seasonality of atmospheric fluxes (higher values during the cold season), highlights the ‘dynamic’ character of the airshed, determining different contaminant loads in the aquatic system depending of its status.; JRC.H.1-Water Resources

Polychlorinated Biphenyls (PCBs) Atmospheric Concentrations and Deposition in Sub-Alpine Northern Italy

CASTRO-JIMÉNEZ Javier; DUERI S.; EISENREICH S.j.; MARIANI Giulio; SKEJO Helle; UMLAUF Gunther; ZALDIVAR COMENGES Jose'
Fonte: Society of Environmental Toxicology and Chemistry (SETAC) Publicador: Society of Environmental Toxicology and Chemistry (SETAC)
Tipo: Contributions to Conferences Formato: CD-ROM
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Atmospheric transport and deposition are important processes determining the fate of many persistent organic pollutants (POPs) in the environment. Research has been carried out in the last decades on ambient concentrations and controls of numerous POPs families. Experimental measurements alone (active and passive sampling) or combined with model estimations have been used to study the POPs environmental processing, transport and behavior in specific regions. However, there are many areas for which little or no information on POPs ambient levels is available. Such is the case with Southern-Western Europe, that remains uncovered by the EMEP POPs monitoring network. Moreover, the scarcity of consistent experimental data sets on atmospheric concentrations poses a problem for proper validation of models. Our main objective was to initiate POPs atmospheric measurements (weekly resolution) in order to assess air concentrations and seasonal variations of selected POPs in a sub-alpine location where little information is available on POPs ambient levels. To achieve this goal, a monitoring and research station was set up at the Joint Research Centre EMEP site (Ispra, Italy). We present and discuss a one year data set (2005-2006) on PCB air concentrations (gas and particulate phases). ¿7PCBs monthly averaged concentration varied from 31-76 pg m-3. These values are within the range of those reported for rural...

Atmospheric concentrations and deposition of polycyclic aromatic hydrocarbons to the Mid-Atlantic East Coast region

Gigliotti, Cari L.; Totten, Lisa A.; Offenberg, John H.; Dachs, Jordi; Reinfelder, John R.; Nelson, Eric D.; Glenn, Thomas R.; Eisenreich, Steven J.
Fonte: American Chemical Society Publicador: American Chemical Society
Tipo: Artículo Formato: 22195 bytes; application/pdf
Português
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57.633237%
10 pages, 3 figures.-- PMID: 16124286 [PubMed].-- Printed version published Aug 1, 2005.; Atmospheric concentrations of polycyclic aromatic hydrocarbons (PAHs) were measured at urban/industrial, suburban, coastal, and rural areas in New Jersey as part of the New Jersey Atmospheric Deposition Network. Concentrations of 36 PAH compounds were measured in the gas and particle phases in air and in precipitation at nine sites at regular intervals from October 1997 through May 2001. Gas-phase and particle-phase Σ36PAH concentrations ranged from 0.45 to 118 ng m-3 and from 0.046 to 172 ng m-3, respectively, and precipitation concentrations ranged from 11 to 16200 ng L-1. PAH concentrations vary spatially across the region, with the highest concentrations occurring at the most heavily urban and industrial locations. Average gas absorption deposition ranged from 0.004 (naphthacene) to 5040 (methylphenanthrenes) ng m-2 d-1, and dry particle deposition PAH fluxes ranged from 0.11 (naphthacene) to 300 (benzo[b+k]fluoranthene) ng m-2 d-1 at the nine sites. Average atmospheric wet deposition PAH fluxes at the seven sites ranged from 0.40 (cyclopenta[cd]pyrene) to 140 (methylphenanthrenes) ng m-2 d-1. These represent the first comprehensive estimates of PAH deposition to New Jersey and the Mid-Atlantic East Coast.; This study was supported by the New Jersey Department of Environmental Protection and the National Sea Grant College Program of the U.S. Department of Commerce's National Oceanic and Atmospheric Administration under NOAA Grant No. NA76-RG0091 (NJSG-05597).; Peer reviewed

Atmospheric concentrations and deposition of polychorinated biphenyls to the Hudson River Estuary

Totten, Lisa A.; Gigliotti, Cari L.; VanRy, Daryl A.; Offenberg, John H.; Nelson, Eric D.; Dachs, Jordi; Reinfelder, John R.; Eisenreich, Steven J.
Fonte: American Chemical Society Publicador: American Chemical Society
Tipo: Artículo Formato: 22195 bytes; application/pdf
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67.74254%
6 pages, 3 figures, 1 table.-- PMID: 15180052 [PubMed].-- Printed version published May 1, 2004.-- Supporting information available at: http://pubs.acs.org/doi/suppl/10.1021/es034878c; The first estimates of atmospheric deposition fluxes of polychlorinated biphenyls (PCBs) to the Hudson River Estuary are presented. Concentrations of PCBs were measured in air, aerosol, and precipitation at nine sites representing a variety of land-use regimes at regular intervals from October 1997 through May 2001. Highest concentrations in the gas phase were observed at urban sites such as Camden and Jersey City (∑PCB concentrations averaged 3250 and 1260 pg m-3, respectively). In great portions of the state encompassing forested, coastal, and suburban environments, gas-phase ∑PCB concentrations were essentially the same (averaging 150−220 pg m-3). This spatial trend suggests that atmospheric PCBs arise from highly localized, urban sources which influence atmospheric concentrations and deposition fluxes over a distance of a few tens of kilometers. Atmospheric ∑PCB deposition fluxes (gas absorption + dry particle deposition + wet deposition) ranged from 7.3 to 340 μg m-2 yr-1 and increased with proximity to urban areas. While the magnitude of the fluxes increased with urbanization...

Passive sampling of atmospheric organochlorine compounds by SPMDs in a remote high mountain area

Van Drooge, Barend L.; Grimalt, Joan O.; Booij, Kees; Camarero, Lluís; Catalán, Jordi
Fonte: Elsevier Publicador: Elsevier
Tipo: Artículo Formato: 22195 bytes; application/pdf
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10 pages, 3 figures.-- Printed version published Sep, 2005.; Semi-permeable membrane devices (SPMDs) have been deployed in high mountain areas (Central Pyrenees, Catalonia, Spain) for the measurement of atmospheric concentrations of hexachlorobenzene (HCB) and polychlorobiphenyls (PCBs) over a period of 1.5 years. These devices were filled with triolein and have been deployed at three altitudes, 1600, 2240 and 2600 m above sea level. Performance reference compounds were used to calibrate their sampling rates.; The SPMD results were validated by comparison to active air sampling with high-volume systems. Sampling rates between 0.55 and 1.3 m3 d−1 were estimated from the dissipation of PCB155. Atmospheric concentrations measured by SPMDs were in good agreement with the levels obtained by high-volume sampling. These findings suggest that SPMDs can be useful monitoring systems for the atmospheric concentrations of organochlorine compounds in remote high mountain areas.; Financial support from the EU projects EUROLIMPACS (GOCE-CT-2003-505540) and EMERGE (EVK1-CT-1999-00032) is acknowledged.; Peer reviewed

Mathematical modeling of atmospheric fine particle-associated primary organic compound concentrations

Rogge, Wolfgang F.; Hildemann, Lynn M.; Mazurek, Monica A.; Cass, Glen R.; Simoneit, Bernd R. T.
Fonte: American Geophysical Union Publicador: American Geophysical Union
Tipo: Article; PeerReviewed Formato: application/pdf
Publicado em 27/08/1996 Português
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An atmospheric transport model has been used to explore the relationship between source emissions and ambient air quality for individual particle phase organic compounds present in primary aerosol source emissions. An inventory of fine particulate organic compound emissions was assembled for the Los Angeles area in the year 1982. Sources characterized included noncatalyst- and catalyst-equipped autos, diesel trucks, paved road dust, tire wear, brake lining dust, meat cooking operations, industrial oil-fired boilers, roofing tar pots, natural gas combustion in residential homes, cigarette smoke, fireplaces burning oak and pine wood, and plant leaf abrasion products. These primary fine particle source emissions were supplied to a computer-based model that simulates atmospheric transport, dispersion, and dry deposition based on the time series of hourly wind observations and mixing depths. Monthly average fine particle organic compound concentrations that would prevail if the primary organic aerosol were transported without chemical reaction were computed for more than 100 organic compounds within an 80 km × 80 km modeling area centered over Los Angeles. The monthly average compound concentrations predicted by the transport model were compared to atmospheric measurements made at monitoring sites within the study area during 1982. The predicted seasonal variation and absolute values of the concentrations of the more stable compounds are found to be in reasonable agreement with the ambient observations. While model predictions for the higher molecular weight polycyclic aromatic hydrocarbons (PAH) are in agreement with ambient observations...

An assessment of the atmospheric nitrogen budget on the South African Highveld

Collett,Kirsten S.; Piketh,Stuart J.; Ross,Kristy E.
Fonte: South African Journal of Science Publicador: South African Journal of Science
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2010 Português
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Atmospheric reactive nitrogen concentrations on the South African Highveld have become a growing concern, with satellite images indicating very high nitrogen dioxide (NO2) concentrations in the region. This study investigated the nitrogen budget on the Highveld through the analysis of the concentration of the atmospheric nitrogen species on a temporal scale as well as the atmospheric conversion, transport and removal of these species. Data were collected at Eskom's Elandsfontein ambient air quality monitoring site, which is centrally located on the industrialised Highveld. A year's dataset from 2005 and 2006 was analysed and it was found that nitrogen oxide (NOx) concentrations were higher in winter as a result of stable atmospheric conditions, as well as prevalent westerly and north-westerly airflow, which transported emissions directly from the nearby power station sources to the monitoring site. Nitrate (NO3) concentrations also peaked during winter, with a distinct biomass burning peak during August 2005. Diurnally, NOx concentrations indicated a tall-stack industrial source, where concentrations peaked at midday. The NO3 concentrations were higher at night than during the day; during the day the NO3 radical is rapidly photolysed and nitrates cannot be produced. Case studies indicated that the conversion rate of nitric oxide (NO) to NO2 was highly variable as a result of varying atmospheric factors...